1. Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method and apparatus of composing an uplink control channel in a wireless communication system.
2. Related Art
The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
One of the systems which are being taken into consideration in the next-generation wireless communication system is an Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) system capable of attenuating an Inter-Symbol Interference (ISI) effect with low complexity. The OFDM system transforms serial input data symbols into N parallel data symbols and transmits the N data symbols on respective N subcarriers. The N subcarriers maintain orthogonality in the frequency domain. The orthogonal channels experience independent frequency selective fading, and the interval between transmitted symbols is lengthened, thereby being capable of minimizing the ISI effect. Orthogonal Frequency Division Multiple Access (hereinafter referred to as OFDMA) refers to a multi-access method of realizing multi-access by independently providing users with some of available subcarriers in a system using OFDM as a modulation method. In the OFDMA method, frequency resources called subcarriers are provided to each user and are independently provided to a number of the users. Accordingly, the frequency resources provided to a number of the users, in general, do not overlap with each other. Consequently, the frequency resources are exclusively allocated to the respective users.
In the OFDMA system, the frequency diversity for a number of users can be obtained through frequency selective scheduling, and subcarriers can be allocated in various manners according to a permutation method for the subcarriers. Further, the efficiency of a space domain can be increased through a space multiplexing scheme using multiple antennas.
To obtain the frequency diversity when transmitting an uplink control signal, there is a need for a method of efficiently composing uplink control channels.